Some of the questions expectant mothers ask most frequently pertain to the developmental changes their babies are undergoing during each month of pregnancy.

The developmental timeline that follows is intended to share what most pregnant women experience. It’s important to note that not all expectant moms have the same experience over the nine months. If you have a concern during your pregnancy, you should reach out to your healthcare provider for advice.

Conception/Month 1
Generally, fertilization happens about two weeks before menstruation would have otherwise occurred. Once a sperm penetrates an egg, the coating of the egg will actually change in an effort to prevent additional sperm from penetrating the egg.

Interestingly, all of the genetic information needed to produce your baby is available as soon as the sperm penetrates the egg. In fact, the sex of your baby is determined right as that happens.

During the first month after conception, there is a rapid and exponential growth of your baby. In fact, if growth were as fast during the rest of your pregnancy as it is during the first month, your baby would grow to be about ten tons!

Toward the end of the first month, some facial features — such as the eyes, the nose and the jawline — can be identified, and a basic circulatory system, including red blood cells, begins to form. By the end of the first month, your baby is about the size of a grain of rice.

Month 2
At this point, your baby is about 10,000 times larger than at conception. The facial features continue to develop and the ears begin to form. For the first time, you can also see the tip of your baby’s nose. The second month of pregnancy is a very exciting time because your baby’s pancreas, liver, spleen and other gastrointestinal organs will form and begin to develop.

Generally, by the end of the second month, your baby will weigh about as much as a peanut.

Month 3
One of the most exciting developments during the third month is the beginning of motor movements by your baby. In fact, your baby won’t likely remain still for more than five minutes at a time! Some of these movements include opening the hands, moving the fingers, etc.

Although your child’s reproductive organs begin to develop, you rarely will be able to identify them via ultrasound at this point.

Toward the end of the third month, the sensory system has developed to the point that loud noises in the environment can startle your baby. In fact, some evidence has suggested that playing calm music near your belly can actually help to soothe your child.

Once you have progressed to the end of your third month, most of the organ systems are so well developed that the risk of miscarriage drops significantly.

Month 4
Your baby’s heart and blood vessels have now completely formed. In fact, the heart rate can now be found with an instrument called a doppler. Also, your baby has now developed unique fingerprints.

By the end of the fourth month, most babies are around six inches long. You may begin to feel fatal movements.

An ultrasound is generally performed at 20 weeks to ensure that the placenta is developing well. For the first time, your child’s sex can be visualized. If you’re lucky, you may be able to catch your baby sucking his thumb, making faces or yawning during an ultrasound.

Month 5
One of the biggest developments during the fifth month is hearing. Most expectant mothers will also begin to notice that their babies’ movements will increase in both frequency and intensity, as tiny muscles continue to develop during this month.

Hair also develops. In addition, a white, cheesy substance known as vernix begins to coat your baby’s skin to protect your child for the rest of the pregnancy. This substance is frequently still seen on a newborn’s skin after delivery.

Month 6
One of the most exciting developments during the sixth month is your baby’s ability to respond to sounds or stimuli. Also, many expectant moms say they begin noticing jerking movements by their babies. Frequently, these movements are a result of a baby having the hiccups.

Some babies who have developed past 23 weeks can survive with intensive care in the NICU if delivered prematurely.

Month 7
By this point, your baby’s skin will actually appear to be wrinkled from spending so much time floating around your amniotic fluid. This month’s biggest development is the accumulation of fat deposits underneath your baby’s skin, which help to keep your baby warm following delivery.

During the seventh month, expectant moms will frequently say that they occasionally feel contractions. Called Braxton-Hicks, these contractions are normal and not dangerous to your baby. They are simply a sign that your body is preparing for delivery. Once a pregnancy has progressed to the end of the seventh month, most babies will be able to survive if born prematurely.

Month 8
A baby’s sensory system has developed so much at this point that some expectant mothers can identify three separate behavioral states: sleeping, being awake and crying. Your baby will also gain the ability to see and hear.

An extremely important developmental chemical called surfactant, which helps your baby’s lungs to develop, is also produced during this month.

By the end of the eighth month, except for the lungs, most of your baby’s organs have almost fully developed.

Month 9
During the beginning of the ninth month, your baby’s neurologic system has developed to the point that your baby gains reflexes, opening and closing his eyes to the light and responding to light and touch.

Your baby will gain about one-hand pound per week during the ninth month.

One of the most frequent concerns at this point in pregnancy is feeling as though your baby isn’t moving as much. This is totally normal (as long as you still feel your baby moving regularly). This is important as the amount of space available for your baby to move has decreased with continued growth.

Although by the end of the ninth month your child is well-developed and ready to enter the world as far as the organs and neurologic systems are concerned, the immune system is still lagging behind. In fact, up until the day of delivery, your baby still receives a large amount of the immune system from you through the placenta. Breastfeeding is important to ensure that your baby has adequate immune system support as the immune system continues to develop after the birth.

Shane Drahos, MD, is a doctor in family medicine, practicing in Fort Myers, FL.